Pancreatic paraganglioma: An extremely rare entity and crucial role of immunohistochemistry for diagnosis
A 55-year-old lady presented to our hospital with a complaint of epigastric discomfort and swelling in left side of the abdomen for preceding 3 months along with slight dragging sensation. Her family history and past history was unremarkable. The physical examination of abdomen revealed a palpable, non-tender lump over left hypochondrium extending up to midline and mild tenderness in epigastrium. No palpable lymphadenopathy of supraclavicular, cervical, and inguinal region were detected. She was normotensive. Her total blood count was within normal limit, except low hemoglobin level. Biochemical investigations for urea, creatinine, and RBS showed normal physiological values. Urine examination for vanil mandelic acid (VMA) was within normal limits. Liver function tests and Chest X-ray were normal. The Ultrasonography revealed a lesion in the tail of pancreas with differential diagnosis of pancreatic malignancy and metastatic tumor. Further imaging by CECT revealed the lesion as multicystic, size of 17 cm × 19 cm [] with an impression of a malignant pancreatic tumor. In color Doppler study, the tumor appeared to be highly vascular. The patient underwent exploratory laparotomy. On gross examination, the tumor was well-circumscribed, round, like a football with glistening surface reddish-brown in color and measured 17 cm × 19 cm. On cut section, the tumor revealed a thickened capsule of size 1.2 cm. The entire tumor mass underneath the capsule showed extensive necrosis, cystic, and hemorrhagic areas []. Microscopically, the tumor composed of oval to round cells arranged in an organoid and trabecular pattern, separated by a delicate vascular network, giving an appearance of classic Zellballen pattern []. The tumor cells have abundant acidophilic cytoplasm containing granules with moderate variation in size and shape and insignificant mitosis. Areas of variable necrosis and hemorrhage were noted []. Immunohistochemistry for chromogranin A showed characteristic punctate pattern of staining by cytoplasmic granules of tumor cells [] and S-100 nuclear immunoreactivity shown by thin lining of sustentacular cells encircling the nests. The cytokeratin was non-reactive and Ki67 labeling was <2%. Therefore, morphology, immunohistochemical features were consistent with extra adrenal paraganglioma. The patient's post-operative course was unremarkable. There was no evidence of disease recurrence at 10 months of follow up with ultrasonography post-operatively.