Small cell carcinoma of the anus in the setting of prior squamous dysplasia and carcinoma in situ

Genomic evidence suggests that cutaneous neuroendocrine carcinomas can arise from squamous dysplastic precursors

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma without a known dysplastic precursor. In some cases, MCC is associated with SCCIS in the overlying epidermis; however, the MCC and SCCIS populations display strikingly different morphologies, and thus far a relationship between these components has not been demonstrated. To better understand the relationship between these distinct tumor cell populations, we evaluated 7 pairs of MCC-SCCIS for overlapping genomic alterations by cancer profiling panel. A subset was further characterized by transcriptional profiling and immunohistochemistry. In 6 of 7 MCC-SCCIS pairs there was highly significant mutational overlap including shared TP53 and/or RB1 mutations. In some cases, oncogenic events previously implicated in MCC (MYCL gain, MDM4 gain, HRAS mutation) were detected in both components. Although FBXW7 mutations were enriched in MCC, no gene mutation was unique to the MCC component across all cases. Transcriptome analysis identified 2736 differentially expressed genes between MCC and SCCIS. Genes upregulated in the MCC component included Polycomb repressive complex targets; downregulated transcripts included epidermal markers, and immune genes such as HLA-A. Immunohistochemical studies revealed increased expression of SOX2 in the MCC component, with diminished H3K27Me3, Rb, and HLA-A expression. In summary, MCC-SCCIS pairs demonstrate clonal relatedness. The shift to neuroendocrine phenotype is associated with loss of Rb protein expression, decrease in global H3K27Me3, and increased expression of Merkel cell genes such as SOX2. Our findings suggest an epidermal origin of MCC in this setting, and to our knowledge provide the first molecular evidence that intraepithelial squamous dysplasia may represent a direct precursor for small cell carcinoma.

Locally advanced anal small cell carcinoma with durable complete response to chemoradiation followed by consolidation chemotherapy: case report and literature review

Extrapulmonary small cell carcinoma (EPSCC) is a rare and aggressive clinical entity that can involve a variety of anatomic locations, including the gastrointestinal tract. Involvement of the gastrointestinal tract is associated with a particularly poor prognosis with patients often presenting with widespread dissemination on initial clinical presentation or rapidly progressing to systemic disease from locoregional involvement. Primary small cell carcinoma of the anal canal is extremely rare, with limited published case reports in the literature. As a result, management of this disease is not well defined, and outcomes are poor with high rates of disease relapse. We report a patient with locally advanced anal small cell carcinoma after presenting with irregular bowel movements, changes in stool caliber, and rectal bleeding for two months and achieved a durable complete response to concurrent chemoradiation with cisplatin and etoposide followed by consolidation chemotherapy and discuss our current understanding of this disease. Specifically, we review the epidemiology, risk factors, clinical course, the treatment strategies over the past two decades, and prognosis for EPSCC. Finally, we conclude our discussion by reviewing the rationale of our treatment regimen and the potential role and benefit of consolidation therapy in the management of this rare and aggressive disease.

High-grade neuroendocrine small-cell carcinoma of the anal canal: Long-term remission with chemoradiotherapy

Primary small-cell carcinoma of the anal canal is an exceedingly rare tumor with a poor prognosis even when aggressive therapy is initiated. We present the case of a 53-year-old male patient who presented with chronic anal pain. Examination under general anesthesia revealed the presence of a mass in the anal canal. A biopsy was performed, and histopathological examination showed a high-grade neuroendocrine small-cell carcinoma. Assessment with endoscopic ultrasound showed an invasion of the internal anal sphincter. The patient was treated with a chemoradiotherapy (CRT) regimen consisting of cisplatin and etoposide, combined to radiotherapy. The patient achieved long-term remission with CRT. This is one of the first reports in the literature of a case of a high-grade neuroendocrine small-cell carcinoma of the anal canal where long-term remission was achieved with non-surgical management of a tumor invading the anal sphincter. This favorable evolution with CRT suggests that remission could still be achieved with anal small-cell carcinomas. More cases are however required to validate this approach.

RELEVANCE FOR PATIENTS

This case presentation suggests that long-term remission can still be achieved using CRT and without an extensive surgical resection in patients with small-cell carcinoma of the anal canal.

Metachronous presentation of small-cell rectal carcinoma on an 18F-FDG PET/CT follow-up for follicular lymphoma

We present a case of a 60-year-old woman with history of follicular lymphoma in remission presenting for an 18F-fluorodeoxyglucose positron emission tomography/computed tomography for suspected recurrence. Imaging showed widespread hypermetabolic lymphadenopathy consistent with lymphoma recurrence. A 3-month 18F-fluorodeoxyglucose positron emission tomography/computed tomography follow-up after chemotherapy showed resolution of hypermetabolic lymphadenopathy but multiple new hepatic lesions and a new subtle rectal lesion. Biopsies of both hepatic and rectal lesions revealed new diagnosis of metachronous high-grade small-cell carcinoma.