Multifocal hyperplasia of interstitial cells of Cajal (ICC hyperplasia) is a precursor of hereditary gastrointestinal stromal tumors (GISTs) in patients with germline mutations of c-KIT or PDGFRA, but precursor lesions of sporadic GISTs have not been defined yet. Small hyalinizing stromal tumors of the proximal stomach (referred to in this study as GIST tumorlets) were collected prospectively from 98 consecutive autopsies and additional cases were retrieved from surgical pathology files (total n=57). GIST tumorlets were grossly detectable in 22.5% consecutive autopsies performed in individuals older than 50 years. All lesions were located in the cardia, fundus, or proximal body, and ranged in size from 1 to 10 mm (4 mm). Similar lesions were not detected in the antrum, duodenum, and the remainder of the bowel. Histologically, the spindle cell subtype comprised all cases, with hyalinization and calcification in 57% of cases. The spindle cells were immunohistochemically positive for vimentin, CD117, and CD34. Twenty-four cases yielded sufficient DNA for subsequent molecular analysis, which showed c-KIT mutations in 11 cases (46%) and PDGFRA mutations in 1 case (4%). Sporadic GIST tumorlets of the proximal stomach are common in the general population over the age of 50 years and frequently show somatic c-KIT mutations. GIST tumorlets probably represent the grossly recognizable counterpart of sporadic ICC hyperplasia caused by somatic c-KIT or PDGFRA mutations. Early hyalinization and calcification seems to confer limited growth potential, and complete regression of such lesions is common. GIST tumorlets likely represent preclinical (preneoplastic) lesions that need additional stimuli to evolve into clinical GISTs, raising the possibility of a hyperplasia-neoplasia sequence in the development of sporadic GISTs.

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Down-regulation of the immune system facilitates tumor progression at different stages of cutaneous melanoma. Sentinel nodes, the first lymph nodes on lymphatics draining directly from a primary melanoma are immune down-regulated by tumor-generated immune-suppressive cytokines including interleukin-10. To better understand the kinetics of sentinel node suppression, we investigated interleukin-10 expression by melanoma cells and tumor-associated macrophages and lymphocytes at different stages of primary melanoma evolution. We used reverse transcriptase in situ polymerase chain reaction to identify cellular sources of interleukin-10 mRNA in 39 melanomas. Interleukin-10 mRNA was identified in tumor cells of 2/6 melanomas in situ (33%), 17/21 invasive melanomas (81%) and 11/12 metastatic melanomas (92%). Higher interleukin-10 expression correlates with tumor progression, with differences between melanoma in situ, invasive melanoma and metastatic melanoma. In primary melanomas, the interleukin-10 mRNA content of tumor cells correlates with Clark level. There was significantly more interleukin-10 mRNA in vertical growth phase melanoma cells than in radial growth phase cells. In a logistic regression model, moderate to high interleukin-10 mRNA expression by tumor cells was significantly associated with vertical growth phase melanoma. Interleukin-10 mRNA was detected in melanoma-associated macrophages and lymphocytes. In invasive melanomas, the interleukin-10 mRNA reactivity of macrophages declined as Clark level increased. Alterations of immunity by interleukin-10 derived from melanoma cells and melanoma-associated macrophages and lymphocytes potentially facilitate evolution of the primary melanoma and render regional lymph nodes susceptible to metastases.

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The proposed culture system supports enrichment and survival of limbal stem and progenitor cells during the entire cultivation process and may be essential for long-term restoration of the damaged ocular surface.