Mammary-type Myofibroblastoma with Leiomyomatous Differentiation: A Rare Variant with Potential Pitfalls.

Myofibroblastoma is a rare, benign stromal tumor with a diverse morphologic spectrum. Mammary-type myofibroblastoma (MTMF) is the extra-mammary counterpart of this neoplasm and its occurrence throughout the body has become increasingly recognized. Similar morphologic variations of MTMF have now been described which mirror those seen in the breast. We describe a case of intra-abdominal MTMF composed of short fascicles of eosinophilic spindle cells admixed with mature adipose tissue. The spindle cells stained diffusely positive for CD34, desmin, smooth muscle actin, and h-caldesmon by immunohistochemistry. Concurrent loss of RB1 (13q14) and 13q34 loci were confirmed by fluorescence in situ hybridization whereas anchored multiplex PCR and whole transcriptome sequencing did not reveal any pathognomonic fusions suggesting an alternative diagnosis. To the best of our knowledge this is the first documented case of leiomyomatous variant of MTMF.

A Novel Case of Mammary-Type Myofibroblastoma With Sarcomatous Features.

Mammary-type myofibroblastoma (MFB) is a benign spindle cell tumor of the breast and soft tissue characterized by 13q14 alterations leading to loss of Rb-1 protein expression, a feature shared among spindle cell lipoma and cellular angiofibroma. In this article, we present a novel case of MFB arising in the left breast of a 70-year old man that microscopically showed an abrupt transition from classic MFB morphology to an area with cytologic atypia and mitotic activity, akin to sarcomatous transformation described in cellular angiofibromas. A thorough workup of the molecular underpinnings of both components using chromosomal microarray and next-generation sequencing platforms supported a clonal relationship. Nearly identical copy number changes, including a single copy loss of 13q14, were found in both components; in addition, the sarcomatous component harbored biallelic TP53 alterations. It is important for pathologists to recognize that sarcomatous features can occur in mammary-type MFB to arrive at the correct diagnosis.

Biomarkers to diagnose metastatic breast carcinoma to the pancreas: A case report and update.

The patient is a 72-year-old female who presents with new onset jaundice. The patient has a past medical history significant for right-sided estrogen receptor (ER)-positive and left-sided ER-negative breast cancers in 2005 and 2009, respectively, and recent 1-year history of ER-positive right-sided breast cancer with bone and brain metastases. CT scan and endoscopic ultrasound (EUS) revealed a new 2 cm mass in the head of the pancreas, leading to EUS-guided fine-needle aspiration of the lesion. Pathologic workup revealed adenocarcinoma with signet-ring cells, representing either metastatic breast or primary pancreatic cancer. Immunohistochemistry and molecular diagnostic workup identified positive GATA-binding protein 3 (GATA3) immunoreactivity and a mutation in Erb-B2 receptor tyrosine kinase 2 (ERBB2), also known as human epidermal growth factor receptor 2 (HER2). Here, we review the diagnostic markers commonly used to differentiate metastatic breast vs primary pancreatic adenocarcinoma, and discuss the challenges of utilizing GATA3 immunoreactivity and ERBB2 mutations for diagnosis.

Pancreatic mixed acinar-neuroendocrine carcinoma, a unique diagnostic challenge on FNA cytology: A small series of two cases with literature review.

Mixed acinar-neuroendocrine carcinoma (MANEC) of the pancreas is a rare tumor. We present two cases of MANEC diagnosed on endoscopic ultrasound (EUS) guided fine-needle aspiration (FNA). The first patient is a 33-year-old male who had a 3.6 cm mass in the uncinate process and liver metastasis. The second patient is a 66-year-old male with a 10 cm mass in the pancreatic tail. The FNA smears from both cases were hypercellular with neoplastic cells in loosely cohesive clusters and many naked nuclei. In both cases, the tumor cells were positive for CKAE1/3, synaptophysin, chromogranin, and trypsin by immunohistochemistry. Final diagnoses of MANEC were rendered based on cytological features and immunohistochemical profiles. To date, 44 cases of MANEC have been reported in the English literature, only three of which were diagnosed on cytopathology specimens before surgical resection. Our report adds two more cases diagnosed on cytopathology alone. Herein, we discuss the various cytomorphologic and clinical features of MANEC and present a brief review of the literature. Diagn. Cytopathol.