Metastatic appendiceal goblet cell carcinoid masquerading as mucinous adenocarcinoma in effusion cytology: A diagnostic pitfall
A 45-year-old female presented with one-month history of gradual distension of abdomen and vomiting. Clinically, gross ascites was present. Past history of patient revealed that three years back, the patient was operated for bilateral ovarian tumor in a private hospital. She was asymptomatic for the next three years. The slides of ovarian tumor were reviewed, and a diagnosis of bilateral mucinous cystadenoma was made. There was no component of invasive tumor or carcinoid component in the ovarian tumor. Computed tomography (CT) scan of abdomen was done, which revealed ascites and diffuse omental thickening. Ascitic fluid was tapped. Slides were prepared on Shandon cytocentrifuge. Smears were made on glass slides, which were fixed immediately in 95% alcohol and stained by Papanicolaou method. Air-dried smears were stained by May-Grünwald-Geimsa (MGG) method. Smears of ascitic fluid were moderately cellular and composed of numerous cells disposed in acini, clusters as well as lying singly in a background of mucin. There were gland-like formations, some with central lumina. Predominant cell type was the signet ring cell with abundant vacuolated cytoplasm and nucleus pushed to periphery. A second population of cells was identified, which were smaller in size with folded nuclei, fine chromatin and scant to moderate amount of eosinophilic cytoplasm []. Our cytological diagnosis was compatible with that of metastatic mucinous adenocarcinoma. In view of a primary ovarian tumor and fluid cytology findings of metastatic mucinous adenocarcinoma, patient was given six cycles of chemotherapy. Repeat computed tomography (CT) scan after six months did not show any significant change in size of omental thickening. Infracolic omentectomy along with appendicectomy was performed. Gross examination of the specimen of appendix revealed a small diffuse shiny thickened area (less than 1 cm) at the tip of appendix. Hematoxylin and eosin-stained sections were obtained from formalin-fixed, paraffin–embedded tissue blocks, which revealed a submucosal infiltrate of dual population of cells, majority of which comprised of classical carcinoid tumor cells and a minor component of GCC lying in a pool of mucin. Mitosis was occasional. Necrosis was not seen. Tumor infiltrated upto peri-appendiceal fat. Sections from the omental thickening revealed infiltration by goblet cells (signet cells) only. Histopathological diagnosis of combined classical carcinoid and GCC with metastases to omentum was made. Immunohistochemical studies were performed on a Ventana Benchmark automated stainer on formalin-fixed, paraffin-embedded tissue block from both the sites. Appropriate positive and negative controls were obtained. The antibodies tested were cytokeratin (CK) 20, and the neuroendocrine markers chromogranin, synaptophysin, and neuron-specific enolase. Immunohistochemistry (IHC) in both the classical carcinoid and goblet cell component revealed positivity for neuroendocrine markers. The ascitic fluid smears were re-examined in light of histopathology findings. On carefully reviewing the slides, the second population of cells, which were fewer in number, was identified as classical carcinoid cells []. These were admixed with goblet cells. We could not make a diagnosis of metastatic GCAC to ascitic fluid because of our lack of experience with such a finding on cytological smears coupled with the fact that there was a frank predominance of signet ring cells in the smear. Identification of the classical carcinoid cells in ascitic fluid earlier would have prevented us from misdiagnosing this case.