Immunohistochemistry-guided management of colon-like CUP in a 20-year-old female: a case report

Sumedha Gupta; Saloni Chadha; Dheer Singh Kalwaniya; Bhawuk Dhir

doi:10.18203/2320-1770.ijrcog20250888

Authors

Sumedha Gupta Department of Obstetrics and Gynaecology, VMMC & Safdarjung Hospital, New Delhi, India
Saloni Chadha Department of Obstetrics and Gynaecology, VMMC & Safdarjung Hospital, New Delhi, India
Dheer Singh Kalwaniya Department of Surgery, VMMC & Safdarjung Hospital, New Delhi, India
Bhawuk Dhir Department of Dermatology, Dermadex, East Patel Nagar, New Delhi, India

DOI:

https://doi.org/10.18203/2320-1770.ijrcog20250888

Keywords:

Cancer of unknown primary, Adenocarcinomas, Immunohistochemistry, Colon-like cancer of unknown primary site, FOLFOX

Abstract

Cancer of unknown primary site (CUP) is characterized by metastatic disease without an identifiable primary tumor, even after extensive evaluation. It accounts for approximately 2% of all cancers and is most commonly diagnosed in older adults, with the highest incidence in patients aged 60-75 years. Diagnosis involves clinical, pathological, and imaging evaluations, including PET and immunohistochemical (IHC) staining, to determine tumor lineage and guide treatment. We present a case of a 20-year-old female with a right inguinal mass. Initial evaluation revealed metastatic adenocarcinoma with no primary tumor identified. The patient’s history included a prior breast fibroadenoma excision, and comprehensive diagnostic work-up, including PET scan, was unremarkable. Immunohistochemistry results were consistent with colon-like CUP, and the patient underwent excision of the inguinal node followed by adjuvant chemotherapy with the FOLFOX regimen. CUP treatment and prognosis vary by tumor subtype, with colon-like CUP typically managed using colorectal cancer-specific therapies. This case underscores the importance of IHC in guiding treatment for CUP and highlights the role of site-specific therapy in improving patient outcomes. Further studies are needed to validate treatment strategies in younger patients with CUP.

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