SMARCA4-Deficient Undifferentiated Tumor Diagnosed on Adrenal Sampling
Report of Six Cases Emphasizing Diagnostic Distinction From Adrenocortical Carcinoma
Salam Ashour, MD, Jordan P. Reynolds, MD“, Sanjay Mukhopadhyay, MDª, and Jesse K. McKenney, MD
From the Robert J. Tomsich Institute of Pathology and Laboratory Medicine, Department of Pathology, Cleveland Clinic, Cleveland, OH, USA.
ABSTRACT
Objectives: SMARCA4-deficient undifferentiated tumor has distinct clinicopathologic features. We describe our experience with primary diagnosis on adrenal sampling.
Methods: We collected six SMARCA4-deficient undifferentiated tumors diagnosed on adrenal sampling. Immunostains for SMARCA4, SF-1, inhibin, calretinin, S-100 protein, EMA, and TTF-1 were performed. A control group of 63 primary adrenocortical tumors was also immunostained.
Results: Patients included four men and two women (aged 52-77 years). Five had unilateral adrenal masses and one bilateral (range, 2.4-9.6 cm). Five had pulmonary masses, and one had a midline mediastinal mass. All cases had a monotonous epithelioid appearance and variable rhabdoid morphology. Immunophenotypically, all six cases had loss of nuclear SMARCA4 expression and no staining for SF-1, inhibin, calretinin, or S-100 protein. Variable EMA immunoreactivity was present in four of six cases and focal nuclear TTF-1 expression in one of six. All 63 adrenocortical neoplasms had retained nuclear SMARCA4 expression.
Conclusions: SMARCA4-deficient undifferentiated tumor may present in the adrenal gland, and this series likely represents metastases from thoracic primaries. Because of the frequent absence of lineage marker expression, knowledge of the characteristic clinical pre- sentation, the rhabdoid morphology, and the typical immunophenotype (loss of SMARCA4/ BRG1) allow for appropriate distinction from adrenocortical carcinoma.
INTRODUCTION
The family of aggressive malignant neoplasms characterized by loss of the switch/su- crose non-fermentable (SWI/SNF)-related matrix-associated, actin dependent regulator of chromatin, subfamily A, member 4 (SMARCA4) gene, which has loss of the SMARCA4- encoded protein Brahma-related gene 1 (BRG1) by immunohistochemistry, is well ac- cepted. Primary mediastinal SMARCA4-deficient malignancies were first described by Le Loarer et al1 in 2015 with subsequent series published by Sauter et al2 and Yoshida
KEY POINTS
· SMARCA4-deficient undifferentiated tumor is well described, but primary diagnosis on adrenal sampling has not been addressed.
. These tumors may lack lineage marker expression but have loss of SMARCA4/ BRG1 nuclear expression by immunohistochemistry.
· The combination of characteristic clinical setting, histologic appearance, and immunophenotype is critical to distinction from adrenocortical carcinoma.
KEY WORDS
SMARCA4; BRG1; Carcinoma; Lung; Mediastinum; Thoracic; Adrenal gland
Am J Clin Pathol January 2022;157:140-145 HTTPS://DOI.ORG/10.1093/AJCP/AQAB101
Received: April 5, 2021 Accepted: May 17, 2021 Advance publication: August 31, 2021
Corresponding author: Jesse K McKenney, MD; mckennj@ccf.org.
@ The Author(s) 2021. Published by Oxford University Press on behalf of American Society for Clinical Pathology. All rights reserved. For permissions, please e-mail: journals.permissions@ oup.com
et al.3 All describe presentation with a large thoracic tumor, pre- dominant rhabdoid tumor morphology, and an aggressive clin- ical course with frequent widespread metastatic disease. As the concept of this tumor has evolved, additional cases have been re- ported under the terms malignancy, sarcoma, and carcinoma, 4-9 but recent publications suggest that most represent smoking- related undifferentiated carcinomas based on an admixture of more typical lung carcinoma in some cases, focal expression of epithelial markers, typical smoking history, and genomic fea- tures overlapping with smoking-related lung carcinomas.10 The upcoming edition of the World Health Organization classification will recommend the term thoracic SMARCA4-deficient undiffer- entiated tumor. Regardless of the specific lineage for a given case, these neoplasms are extremely aggressive, and rapid progression with disease-related death is typical. Extrathoracic metastases may be seen at presentation, most commonly involving lymph nodes, bone, and adrenal glands. Because spread to the abdomi- nal cavity is described in a subset of cases (including peritoneum, omentum, and mesentery), these neoplasms may present as dis- seminated intra-abdominal malignancies of uncertain primary site. We describe our experience with primary diagnosis on tis- sue samples from a dominant adrenal mass to address morpho- logic and immunophenotypic overlap with typical adrenocortical carcinoma.
MATERIALS AND METHODS
This study was performed under approval of our institu- tional review board (IRB: 14-641). We collected prospective cases diagnosed as SMARCA4-deficient malignancies present- ing on adrenal sampling from our consultation practice from
September 2019 to October 2020. In addition, our surgical pa- thology archives were searched from January 1985 to October 2020 to identify potential cases retrospectively. Clinical and pathologic features were recorded from pathologic materials and medical records provided with the consultation, including patient age, sex, procedure type, lung tumor site and size, adre- nal tumor laterality and size, distribution of other metastases, and smoking history.
Immunostains for SMARCA4/BRG1 (1:300; clone EPNCIR111A; Abcam), steroidogenic factor 1 (SF-1) (1:100; clone N1665; R&D Systems), and epithelial membrane anti- gen (EMA) (1:50; clone E29; Agilent/Dako) were performed on each case. Other immunostains sent from the contrib- uting hospitals during initial workup were rereviewed and results recorded. Immunostains for SMARCA4 (BRG1) and EMA were performed on the Ventana Benchmark Ultra au- tomated immunostainer (Ventana Medical Systems [VMS]). Formalin-fixed, paraffin-embedded tissue sections, cut at 4 pm, were treated with online deparaffinization, fol- lowed by online epitope retrieval, if required. Localization of the antigen-antibody complex was achieved using the VMS OptiView DAB polymer detection kit. Immunostains for SF-1 were performed on the Leica Bond III automated immunostainer (Leica Biosystems). Formalin-fixed, paraffin- embedded tissue sections cut at 4 pm were treated with on- line deparaffinization, followed by online epitope retrieval. Localization of the antigen-antibody complex was achieved using the Leica Bond Polymer Refine DAB detection kit.
A tissue microarray containing 63 adrenal cortical tumors was used as a control group for SMARCA4 immunostaining (one 3-mm core from each tumor).
| TABLE 1 SMARCA4-Deficient Undifferentiated Tumors Presenting in Adrenal Sampling | |||||||
|---|---|---|---|---|---|---|---|
| Patient No. | Age, y | Sex | Smoker | Adrenal Mass, cm | Specimen Type | Thoracic Disease | Intra-abdominal Disease |
| 1 | 52 | M | NA | 6.6 | Needle biopsy | Lung mass, RUL, 6.3 cm | No |
| Right pretracheal adenopathy, 5.1 cm | |||||||
| 2 | 77 | F | Yes | 5.0 | Adrenalectomy | Lung mass, RUL, 8 cm | No |
| 3 | 58 | M | Yes | 9.6 | Needle biopsy | Lung mass, LLL, 4.2 cm | No |
| Invasion of left pulmonary vein and left atrium, multiple smaller lung masses | |||||||
| Mediastinal adenopathy | |||||||
| 4 | 71 | M | Yes | 2.4 | FNA with cell block | Lung masses, LUL, 1.9 cm and 1.5 cm | Liver and peritoneal masses |
| Bilateral hilar adenopathy | Retroperitoneal adenopathy | ||||||
| 5 | 70 | M | Yes | 9 | Radical nephrectomy | Midline mediastinal mass, 5.5 cm | No No |
| Pretracheal adenopathy | |||||||
| 6 | 69 | F | Yes | 6.5 | Needle biopsy | Lung mass, LUL, 1.9 cm | |
| Hilar, pretracheal, and subcarinal adenopathy | |||||||
FNA, fine needle aspiration; LLL, left lower lobe; LUL, left upper lobe; NA, not available; RUL, right upper lobe.
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RESULTS
Five undifferentiated malignancies with SMARCA4 deficiency diag- nosed on adrenal sampling were collected prospectively from our consultation practice, and one additional case was identified from in-house surgical pathology archives. Patients included four men and two women TABLE 1 . Patient age ranged from 52 to 77 years (mean, 66 years; median, 69.5 years). All six patients had an adre- nal mass: three unilateral right-sided (9, 6.6, and 6.5 cm), two uni- lateral left-sided (9.6 and 5 cm), and one bilateral (largest 2.4 cm). Four were sampled by needle biopsy, one by adrenalectomy, and one by radical nephrectomy. Five cases were sent in consultation with a question of primary site of origin to exclude adrenocortical carcinoma, while one retrospective case was originally diagnosed as adrenocortical carcinoma.
Five patients had a simultaneous lung or mediastinal mass, and one was found at surveillance imaging 11 months following prior lung
resection for pT4NOMO “poorly differentiated carcinoma” in a pa- tient with a history of colon (pT3N0M0) and breast adenocarcinoma (pT1N0M0). Four had pulmonary masses, two in the right upper lobe (8 and 6.3 cm), one in the left lower lobe (4.2 cm), and two in the left upper lobe (1.9 and 1.9 cm). One older in-house case had a 5.5-cm mid- line mediastinal mass evaluated on plain-film x-ray only. Other medi- astinal disease was evident on imaging in five of six patients, includ- ing pretracheal adenopathy (n = 3), hilar adenopathy (n = 3), pleural nodules (n = 2), and invasion of pulmonary great vessels (n = 1). In five of six cases, the adrenal mass was larger than the thoracic mass. One patient also had extensive intra-abdominal disease involving liver, ret- roperitoneal lymph nodes, and peritoneum. In five of six patients, a long history of cigarette smoking was well documented; smoking history was unavailable for one patient.
Histologically, all six cases had a similar morphology with a relatively monotonous epithelioid appearance and areas of well-developed but variable rhabdoid morphology characterized
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by round cells, eccentric nuclei with a rim of eosinophilic cyto- plasm, and variable large nucleoli FIGURE 1 . One case had exten- sive necrosis. Immunophenotypically, all six cases showed total loss of nuclear SMARCA4 (BRG1) expression in the neoplastic cells with appropriate internal control staining in nonneoplastic lymphocytes FIGURE 2 . All six cases were completely negative for SF-1, inhibin, calretinin, S-100 protein, CK7, and CK20. Of the cases with available tissue, five of five were negative for p40 and Melan-A, while four of four had retained SMARCB1 (INI-1) nuclear expression. Epithelial marker expression was variable, but four (66%) of six had EMA expression, one (17%) of six had patchy nuclear TTF-1 expression, two (40%) of five expressed focal Cam5.2, and one (17%) of six expressed focal cytokeratin AE1/AE3. One of four cases had strong and diffuse CD34 expres- sion, while three were negative. EMA staining was characterized
by scattered individual neoplastic cells with cytoplasmic ex- pression in three of four positive cases, but one had relatively diffuse staining. The cases with Cam5.2 and cytokeratin AE1/AE3 expression also expressed EMA. Synaptophysin was performed in four of six cases with three showing strong cytoplasmic reac- tivity in greater than 50% of cells.
In the control group of adrenal cortical neoplasms on tissue mi- croarray, all 40 adrenocortical carcinomas and 23 adrenal cortical adenomas demonstrated retained SMARCA4 nuclear expression.
DISCUSSION
The classification of neoplasms with underlying alterations in the SWI/SNF chromatin remodeling complex, mainly SMARCA4
and SMARCB1, has evolved over the past decade with an ex- panding array of tumors recognized.11,12 Originally recognized in a subset of soft tissue sarcomas, alterations in carcinomas are more recently described, including gastrointestinal, pulmo- nary, endometrial, renal, urinary bladder, ovary, and sinonasal primaries.5,13-22 SMARCA4 loss in typical pulmonary adenocar- cinomas has been described and is associated with worsened prognosis.5,22 However, a unique aggressive variant of medi- astinal malignancy characterized by a predominant rhabdoid morphology and SMARCA4 deficiency is now recognized. While originally described as “sarcoma,” authors have recently argued that most cases represent smoking-related undifferentiated carcinomas.1º The term thoracic SMARCA4-deficient undiffer- entiated tumor is now favored. These mediastinal SMARCA4- deficient malignancies often present with bulky tumor burden that may involve mediastinal, intra-abdominal, and retroperi- toneal sites. A recent literature review of 102 documented cases with variable details found that 14 (14%) had adrenal involve- ment and 20 (20%) had other sites of intra-abdominal disease, most commonly involving the liver and peritoneum.10 In the three series that reported more than 10 cases and had detailed descriptions of metastatic sites, the adrenal glands were in- volved in 17%, 17%, and 32% of cases. In the two series with suf- ficient data, nonadrenal intra-abdominal and/or retroperitoneal spread at the time of diagnosis was reported in 41% and 45% of cases. By immunohistochemistry, these tumors have unusual phenotypes distinct from more typical forms of lung adenocarci- noma, including frequent lack or limited expression of TTF-1 and CK7, as well as variable but frequent staining for synaptophysin and CD34.
While lung carcinomas are known for their proclivity to me- tastasize to the adrenal gland, more extensive intra-abdominal spread is unusual and complicates the clinical workup for ana- tomic site of origin. In our experience, the presence of a large ad- renal mass may prompt the clinical consideration of an adrenal primary, particularly when other intra-abdominal or retroperi- toneal disease is present and/or the adrenal gland represents the largest mass. For the surgical pathologist, the rhabdoid morphol- ogy may closely mimic an oncocytic adrenocortical carcinoma. Immunophenotyping is essential in such cases. While inhibin, calretinin, and Melan-A have historically been used as the primary
markers of adrenal cortical lineage, SF-1 is now regarded as one of
the most useful markers in the distinction from other tumors.23-27 In this series, all six cases had an SF-1-negative, inhibin-negative, calretinin-negative, SMARCA4-deficient immunophenotype; five of five tested cases also lacked Melan-A immunoreactivity. The com- bined morphology and immunophenotype are distinct from pro- totypical adrenocortical carcinoma. While one might consider the possibility of primary adrenal SMARCA4-deficient undifferentiated tumors, comprehensive genomic characterization of adrenocortical carcinomas has not revealed SMARCA4 alterations,28 which is sup- ported by the retained SMARCA4 nuclear expression identified in all 40 adrenocortical carcinomas we tested. In addition, to date, there is no documented association between typical adrenocortical
carcinoma and a SMARCA4-undifferentiated component. Finally, lymph node spread from adrenocortical carcinoma typically in- volves the regional nodes from the renal hilum or near the origin of the celiac and mesenteric arteries. Involvement of only medi- astinal lymph nodes in the context of a lung mass would not be typical. Based on the overall pathologic features, the smoking his- tory of the patients, and the thoracic masses with coexisting me- diastinal adenopathy, we would argue that this series represents adrenal metastases from primary thoracic SMARCA4-deficient undifferentiated tumors.
Studies suggest that, despite their aggressive biology, SMARCA4- deficient thoracic tumors may be more responsive to immunother- apy.29 Initial and prolonged responses to pembrolizumab and nivolumab are reported,8,30-32 further underscoring the importance of their appropriate diagnosis.
In summary, SMARCA4-deficient undifferentiated tumors may present as dominant adrenal masses and likely represent metasta- ses from thoracic primaries in this series. Because of limited lineage marker expression by immunohistochemistry, knowledge of the unique clinical presentation, the expected rhabdoid morphology, and the loss of nuclear SMARCA4 (BRG1) expression should allow for better recognition of this distinct entity and appropriate patho- logic distinction from typical adrenocortical carcinoma.
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