Diagnostic clues for differentiating Merkel cell carcinoma from lymphoma in fine‐needle aspiration cytology

Abstract

Nodal fine needle aspiration (FNA) is usually the first procedure in the work-up of malignancy of unknown primary. Merkel cell carcinoma (MCC) is an aggressive cutaneous cancer more common in Caucasians but rare among Asians. It is a diagnostic challenge in evaluating FNA from a metastatic MCC without the knowledge of a current or prior history of skin cancer. We report the case of a Taiwanese male with cervical and axillary masses. The diagnosis of the FNA from the axillary lymph node was lymphoproliferative lesion suspicious for lymphoma. The histopathological evaluation of nodal biopsy revealed a metastatic neuroendocrine carcinoma and the subse-

An Extraordinary Cause of Colonic Obstruction: Merkel Cell Carcinoma of Unknown Primary

“…Negative CDX-2, CK7, TTF-1, and CD45 by immunohistochemistry in conjunction with positive keratin and neuroendocrine stains excluded primary small cell neuroendocrine carcinomas of the small bowel, lung and thyroid, and lymphoma, respectively. 16–18 Unusual, but seen in a small subset of MCCs, CK20 was negative. 17 When most or all keratin stains are negative, a second neuroendocrine stain, such as INMS1 or CD56, may be helpful for confirmation.…”

Pitfalls in soft tissue cytopathology

“…In addition, large numbers of apoptotic bodies are often noted 48 . Rarely, cytoplasmic pale bodies have been reported in MCCs 49 . These morphological features are useful in testing cell block preparations for dot‐like expression of CK20, along with positive immunoexpression of neuroendocrine markers, such as CD56 48 .…”

“…48 Rarely, cytoplasmic pale bodies have been reported in MCCs. 49 These morphological features are useful in testing cell block preparations for dot-like expression of CK20, along with positive immunoexpression of neuroendocrine markers, such as CD56. 48 These features, along with observations of a lack of lymphoglandular bodies and an immunocytochemical profile, are useful in differentiating an MCC from an NHL.…”

“…48 These features, along with observations of a lack of lymphoglandular bodies and an immunocytochemical profile, are useful in differentiating an MCC from an NHL. 49 Rare cases of MCC coexisting with NHL have been reported in the literature. 50 Primary cutaneous lymphomas can mimic soft tissue sarcomas.…”

Combined Merkel Cell Carcinoma with Nodal Presentation: Report of a Case Diagnosed with Excisional but Not Incisional Biopsy and Literature Review

“…(A) An inguinal lymph node biopsy showed complete replacement by metastatic hyperchromatic tumor cells (magnification ×20). (B) Imprint cytology of the lymph node disclosed small-sized neoplastic cells exhibiting an "Indian" filing pattern (arrowhead) and nuclear molding, suggestive of small cell carcinoma or NEC (Liu stain, ×400) [11]. (C) A Romanowsky-stained slide depicted occasional paranuclear blue inclusions (arrow), supporting the diagnosis of NEC or MCC cells (Liu stain, ×1000) [11].…”