Clinicopathological diagnosis of axillary signet-ring cell-like/histiocytoid carcinoma: a case report and literature review.

Objective: To explore the clinicopathological and morphological characteristics, diagnosis, differential diagnosis, treatment, and prognosis of primary signet-ring cell/histiocytoid carcinoma (SRCHC) of the axilla.

Methods: The clinical manifestations, pathomorphological characteristics, and immunohistochemical staining results of a case of primary SRCHC in the axilla were retrospectively analyzed, and the relevant literature was reviewed.

Results: The patient was a 69-year-old male. Subcutaneous gray-white nodules with unclear boundaries were visible. Microscopic examination: The tumor was located in the dermis and subcutaneous tissue. The tumor cells were arranged in a cord-like, soldier-like, or nest-like shape, with mild to moderate atypia. Some cells had obvious nucleoli. The tumor cytoplasm was eosinophilic, and mucoid material inside and outside the cells could be seen, showing a signet-ring-like or histiocytoid appearance. Immunohistochemical staining was positive for GCDFP-15, CK7, E-cadherin, AR, P120, GATA3 and negative for Villin, S-100, CK20, SMA, P63, CD68, TTF-1, NapsinA, ER, PR, and Ki-67 proliferation index (8%), HER2(2+) and FISH(-). The special staining AB-PAS (AB+,PAS-).

Conclusion: Cutaneous axillary primary SRCHC is extremely rare and highly invasive and needs to be differentiated from a variety of metastatic tumors (breast, digestive system, lung, etc.).