Histologic and genomic characterization of a primary mucinous carcinoma of the skin

Abstract

Aims: Primary skin mucinous carcinoma is a rare sweat gland neoplasm with a high local recurrence rate after conventional excision but a low distant-metastasis rate. The genetic underpinning of skin mucinous carcinoma is presently unknown. Here, we sought to define whether the repertoire of somatic mutations of a primary mucinous carcinoma of the skin would be similar to that of mucinous breast carcinomas, given the histologic similarities between these tumor types. Methods and results: The tumor was situated in the dermis and partially involved the subcutaneous fat. Tumor cells were suspended in periodic acid–Schiff diastaseresistant- positive mucin lakes and expressed cytokeratin 7, synaptophysin and estrogen receptor. DNA samples extracted from microdissected tumor and matched normal tissue were subjected to massively parallel sequencing targeting 410 cancer-related genes. The skin mucinous tumor was found to have a low tumor mutation burden, but to harbor a clonal GATA3 frameshift mutation (p.T418Hfs*89) and amplification of FOXA1, genes not uncommonly altered in breast mucinous carcinomas. Conclusions: In this primary skin mucinous carcinoma, GATA3 and FOXA1 driver genetic events were identified, consistent with a possible developmental relationship between skin and breast mucinous neoplasms.

Keywords

• Primary skin mucinous carcinoma
• Targeted sequencing
• Immunohistochemistry