Background: Rare malignancies arising in genetic cancer syndromes, chronic inflammatory states, congenital anomalies, therapy-related settings, and those with unusual paraneoplastic or metastatic patterns represent a distinct, under-reported subgroup Here we are presenting 37 such rare malignancies due to the rarity and for documentation.Methods: This retrospective observational study included 37 patients treated between January 1998 and August 2025 at a tertiary cancer center in Eastern India.Eighteen cases had been previously published and 19 new cases were added.Patients were categorized into: (1) common malignancies arising in rare genetic or acquired predisposing conditions, and (2) common malignancies with rare clinical, biological, paraneoplastic, or metastatic manifestations.Results: Patients with xeroderma pigmentosum (n=6) had squamous, basal cell and malignant melanomas with tongue and ovarian carcinoma, Tuberous sclerosis (n=4) had SEGA and bilateral renal angiomyolipomas.Neurofibromatosis (n=7) had malignant peripheral nerve sheath tumors and intracranial tumors, hereditary multiple exostoses (n=1) had chondrosarcomaa nd Klinefelter syndrome (n=1) had CML.Malignancies arising in chronic states were SCC over burn scars (n=3), filarial scrotum (n=1), tropical ulcer (n=1), adenocarcinoma in ectopia vesicae (n=1).Therapy-related second cancer were meningioma 12 years after childhood ALL and AML 63 months after CTRT for cancer cervix. 2 patients had primary granulocytic sarcoma of meninges and mediastinum.Paraneoplastic syndromes included carcinoma larynx with pemphigus, bronchial carcinoid with ectopic cushing's syndrome and solitary fibrous tumor with hypoglycemia.Rare associations included vanishing bone disease, ectopic male breast cancer on the upper chest wall, synchronous GIST with papillary RCC, synchronous Lobular carcinoma of breast with clear cell carcinoma of right kidney and colonic metastasis from IDC of the breast.Conclusions: Due to the rarity lifelong surveillance, early genetic counseling, prompt evaluation of chronic non-healing lesions, and structured survivorship follow-up are essential to improve outcomes in high-risk populations.
Mentesidou et al. (Sun,) studied this question.