Pulmonary clear cell carcinoid tumor: another entity in the differential diagnosis of pulmonary clear cell neoplasia

Clear cell carcinoid of the appendix: Report of two cases with literature review

The clear cell/lipid-rich change has been described in neuroendocine tumors in several organs, but rarely observed in the appendix. In this study, we describe the morphologic, immunohistochemical features of incidentally discovered appendiceal carcinoids entirely represented by clear cells in a 22-year-old man and a 52-year-old woman. Ultrastructual examination demonstrated abundant lipid droplets and dense core granules. The mechanism leading to lipid accumulation in the cytoplasm has not been discovered, but degenerative processes following recurrent inflammatory change might be considered. This uncommon variant of appendiceal classic carcinoid tumors may bear a superficial resemblance to goblet carcinoid and/or appendiceal metastases from clear cell carcinoma. Awareness of clear cell carcinoid of the appendix will prevent incorrect diagnosis and unnecessary aggressive management.

Lipid-rich ("clear cell") neuroendocrine tumors of the pancreas in MEN I patients

The presence of "clear" or lipid-rich cells within pancreatic neuroendocrine tumors is thought to be pathognomonic of von Hippel-Lindau (VHL) disease, especially in the context of multiple tumors. However, we encountered the presence of lipid-rich cells in six of 16 patients (eight microadenomas/adenomas) who had multiple endocrine neoplasia type I (MEN I). Three of the lesions (two microadenomas and one adenoma) were composed entirely of lipid-rich cells while the remaining five lesions had a component of lipid-rich cells. All lesions containing lipid-rich cells were negative for α-inhibin, but positive for chromogranin and synaptophysin. In addition, four of the eight lesions were glucagon positive. None of the patients had clinical symptoms related to hormone production. We suggest that lipid-rich cells are not reflexly indicative of VHL, and that they may be encountered in a proportion of cases of MEN I either focally or constituting the entire neuroendocrine lesion.

Primary clear cell carcinoid tumors of the vulva

Neuroendocrine tumors are uncommon in the female genital tract and have been described in the ovary, uterus, cervix, and vagina. Primary carcinoid tumors have not been described in the vulva. We report 3 cases in 3 middle-aged women who presented with a solitary vulvar nodule without any other associated symptoms. All were treated with simple local excision. Two tumors were composed exclusively of clear cells arranged in nests separated by fibrovascular septae. The third tumor predominantly exhibited nests of eosinophilic granular cells with scattered areas of cells showing clear cytoplasm. Immunohistochemical staining for chromogranin and neuron-specific enolase confirmed neuroendocrine differentiation in all cases. Follow-up of 5.5 to 16 years showed no evidence of recurrence or metastasis. Primary clear cell carcinoid tumors of the vulva need to be considered in the differential diagnosis of vulvar masses with clear cell features. Immunohistochemistry plays an important role in the diagnosis of these lesions.

Clear cell carcinoid of the appendix: an uncommon variant of lipid-rich neuroendocrine tumor with a broad differential diagnosis

The designation of clear cell/lipid-rich refers to an unusual variant of neuroendocrine tumor ("carcinoid") described in several organs, but only recently observed in the appendix. In this study, we report the morphologic, immunohistochemical, and ultrastructural features of an incidentally discovered appendiceal clear cell/lipid-rich carcinoid in a 32-year-old man without any evidence of von Hippel-Lindau disease. Differential diagnosis with mimicking neoplastic and non-tumor lesions, epidemiology, and clinical behavior of this exceedingly rare variant of carcinoid of the appendix are also discussed.

The use of immunohistochemistry in the diagnosis of metastatic clear cell renal cell carcinoma: a review of PAX-8, PAX-2, hKIM-1, RCCma, and CD10

The diagnosis of metastatic clear cell renal cell carcinoma may be difficult in some cases, particularly in the small image-guided biopsies that are becoming more common. As targeted therapies for renal cell carcinoma are now standard treatment, the recognition and diagnosis of renal cell carcinoma has become even more critical. Many adjunctive immunohistochemical markers of renal epithelial lineage such as CD10 and RCCma have been proposed as aids in the diagnosis of metastatic renal cell carcinoma, but low specificities often limit their utility. More recently described markers (PAX-2, PAX-8, human kidney injury molecule-1, hepatocyte nuclear factor-1-β, and carbonic anhydrase-IX) offer the potential for greater sensitivity and specificity in this diagnostic setting; however, knowledge of their expected staining in other neoplasms and tissues is critical for appropriate use. In this review, we discuss the most widely used immunohistochemical markers of renal lineage with an emphasis on their sensitivity and specificity for metastatic clear cell renal cell carcinoma. Subsequently, we present a variety of organ-specific differential diagnostic scenarios in which metastatic clear cell renal cell carcinoma might be considered and we propose immunopanels for use in each situation.

Lipid-rich variant of appendiceal well-differentiated endocrine tumor (carcinoid)

Well-differentiated endocrine tumors (WDETs) of the appendix show characteristic morphologic features, including proliferation of cells with finely granulated eosinophilic cytoplasm. However, clear cell WDETs, which can present a diagnostic challenge, have been occasionally described, but it is unknown whether they represent a morphologic variant with distinct clinicopathologic features. Moreover, the clear cell appearance of the cytoplasm has never been explained. We studied 13 appendiceal WDETs composed of clear cells, which showed an immunophenotype identical to that of conventional appendiceal WDETs. Ultrastructural examination demonstrated abundant lipid accumulation. Patient survival was excellent and equal to that of conventional appendiceal WDETs. These neoplasms, which represent a lipid-rich variant of appendiceal WDETs, do not have different relevant clinical implications compared with conventional WDETs, but it is important to know of their existence for the differential diagnosis with more aggressive neoplasms, including goblet cell carcinoids and appendiceal metastases from clear cell carcinomas.

Lipid-rich and clear cell neuroendocrine tumors ("carcinoids") of the appendix: potential confusion with goblet cell carcinoid

The so-called clear cell change has been described in neuroendocrine tumors at several locations. Those associated with von Hippel Lindau disease are pathognomonically "clear" and the cytoplasmic appearance has been ascribed to intracytoplasmic lipid. However, lipid has not been demonstrated in all cases of clear cell carcinoid tumors. Such variants have not been described in carcinoid tumors of the appendix and cases with a prominent proportion of clear or more correctly, lipid-rich cytoplasm may bear a superficial resemblance to goblet cell carcinoid and/or signet ring adenocarcinoma. Seven cases, in 5 females and 2 males ranging in age from 22 to 65 years, were noted to have a population of lipid-rich and vacuolated clear cells accounting for 25% or more of the tumor population. The carcinoid tumors were incidental in all cases with 4 of patients presenting with appendicitis, 2 with concomitant mucinous cystadenocarcinomas of the appendix and 1 with an adenocarcinoma of the ascending colon. Morphologically, the tumors had a nested and trabecular pattern and were composed of an admixture of microvesicular and clear lipid-rich cells. There were no mitoses, areas of necrosis of lymphovascular invasion and all cases extended to the mesoappendix. All cases were positive for synaptophysin, chromogranin, and serotonin but negative for inhibin. Three cases were examined ultrastructurally, and showed the presence of intracytoplasmic lipid and neurosecretory granules. None of the patients have shown evidence of recurrent disease. The importance of recognizing this variant of carcinoid tumor in the appendix is to avoid confusion with goblet cell carcinoid tumors with or without a signet ring adenocarcinoma. The presence of multi-vacuolated, foamy and clear cells, some resembling signet ring or goblet cells, in otherwise classic carcinoid tumors is rare but should be considered in this context in the appendix.

Clear cell "sugar" tumor of the lung: a well-enhanced mass with an early washout pattern on dynamic contrast-enhanced computed tomography

Clear cell tumor of the lung is a rare and very unusual benign pulmonary tumor. As clear cell tumor of the lung contains abundant cytoplasmic glycogen, this tumor is called "sugar tumor". We report a case of sugar tumor in a 64-yr-old man presenting as a round pulmonary nodule. On dynamic computed tomography (CT) scans, the solitary pulmonary nodule showed early wash-in enhancement with an early washout pattern like a lung malignancy. The patient underwent wedge resection for the tumor. Pathologic examination, including immunohistochemical studies, revealed that the nodule was a benign clear cell tumor, so-called "sugar tumor". Because only a small number of cases have been reported previously, clinical aspects, radiological characteristics on dynamic contrast-enhanced CT, and differential diagnosis of the tumor are not well established. Herein we present a clear cell tumor of the lung and discuss the clinical, radiological, and pathological features of the tumor.

Clear cell carcinoid tumor of the gallbladder. A case without von Hippel-Lindau disease

A golden yellow polyp was detected in the gallbladder of a 64-year-old man who presented with epigastric pain. The lesion was composed of clear polygonal cells arranged in a trabecular and glandular pattern. The tumor invaded through the wall into the perimuscular subserosal layer. Immunohistochemical stains showed that neoplastic cells were positive for chromogranin A, synaptophysin, somatostatin, gastrin, and pancreatic polypeptide and negative for glucagon, serotonin, insulin, S100 protein, and inhibin. This tumor resembles the recently described clear cell endocrine tumors of the gallbladder and pancreas that are associated with von Hippel-Lindau disease. Our patient, however, had neither personal nor family history indicative of von Hippel-Lindau disease. Furthermore, published accounts of clear cell endocrine tumors in von Hippel-Lindau disease describe immunoreactivity for inhibin; the current case was negative for the disease. There may be a subtype of clear cell carcinoid tumor not associated with von Hippel-Lindau disease, which is characterized by its lack of immunoreactivity against inhibin.

Lipid-rich carcinoid tumor of the thymus gland: diagnosis by fine-needle aspiration biopsy

In this report we describe the cytologic features of an unusual thymic carcinoid tumor containing prominent cytoplasmic lipid vacuoles that was diagnosed by fine-needle aspiration biopsy. The tumor presented as a presternal subcutaneous mass in an 81-yr-old female, with a contiguous mediastinal mass on computed tomography. The cytomorphologic features included numerous discohesive cells with eccentric, round to oval nuclei, granular chromatin, and scant cytoplasm containing numerous intracytoplasmic, clear vacuoles. The neoplastic cells were reactive for neuroendocrine markers by immunocytochemistry and showed reactivity of the intracytoplasmic vacuoles with an oil red-O stain for neutral lipid. Ultrastructural examination confirmed the presence of intracytoplasmic lipid vacuoles and neurosecretory granules. Subsequent surgical excision confirmed the diagnosis. We believe this to be the first report describing these features in a primary thymic carcinoid tumor. The differential diagnosis of mediastinal tumors with clear-cell features and cytoplasmic vacuolization is also discussed.