Solar Elastotic Material in Dermal Lymphatics and Lymph Nodes

Comprehensive Clinical, Histopathologic, and Molecular Analysis and Long-term Follow-up of Patients With Nodal Blue Nevi

Blue nevi are benign, melanocytic neoplasms that show a range of clinical and morphologic patterns and include common/dendritic, cellular, and atypical cellular subtypes. Like other nevi, they most commonly occur in skin but can occasionally involve lymph nodes where they may be misinterpreted as representing metastatic melanoma. Moreover, whether benign blue nevi can metastasize to lymph nodes and their natural history and prognostic significance has been the subject of great controversy. To date, few cases of nodal blue nevi have been reported in the literature, and those reports have had limited clinical follow-up and supporting molecular data. This study sought to determine the clinical, pathologic, and molecular features of blue nevi involving lymph nodes, clarify their clinical significance, provide evidence for understanding their pathogenesis, and highlight potential pitfalls in the interpretation of lymph nodes with an ultimate aim of improving patient care. Thirteen cases of blue nevi involving lymph nodes were identified in the archives of Royal Prince Alfred Hospital, Sydney, Australia (1984-2018). A detailed assessment of the clinical and pathologic features of each case was performed, including an evaluation of all available immunohistochemical stains. Extended clinical follow-up was available for 9 patients. Droplet digital polymerase chain reaction for GNAQ Q209L, Q209P and GNA11 Q209L mutations was performed on 7 cases of blue nevi within lymph nodes together with matching cutaneous (presumed primary) blue nevi in 2 cases. All cases showed typical histologic features of blue nevi. BAP1 was retained in all cases (n=7). There were no recurrence or metastasis of blue nevus in any case on long-term clinical follow-up (n=9, median follow-up, 12 y). The majority of cases (n=5 of 7 evaluated) had GNAQ and GNA11 driver mutations. The 2 patients with a matched primary cutaneous blue nevus and regionally associated nodal blue nevus had the same GNAQ Q209L mutation in both sites in each patient. We conclude that blue nevi can involve lymph nodes and are associated with benign clinical behavior, and probably represent so-called "benign" metastasis. Awareness of these lesions is important when evaluating lymph nodes to avoid misdiagnosis as metastatic melanoma.

Current concepts of ectopic nodal inclusions with special emphasis on nodal nevi

Nodal inclusions of ectopic tissue within lymph nodes are seen comparatively often in dermatopathology and general pathology. Glandular and nonglandular epithelium, as well as melanocytic nevi can be observed within lymph nodes and represent mostly incidental findings without any relevance. The main challenge in reporting these morphologic features is to differentiate such benign inclusions from metastatic settlements of distinct organ tumors. As sentinel node biopsy and lymph node dissection have become standard procedure in clinical oncology and have an immense clinical impact, the correct evaluation of these nodal inclusions is indispensable to avoid undertreatment or overtreatment of patients. In addition, the genesis of these inclusions has not yet been satisfactorily clarified. Two concepts have been laid out: the theory of benign metastases and the migration arrest theory. However, neither theory has so far been able to answer the following questions: Why do we find more nodal nevi in patients with melanoma who had a sentinel node biopsy than in patients without melanoma, and why do we not find nodal nevi in deep visceral lymph nodes? We present a comprehensive review of the current knowledge on nodal inclusions, proposing a concept for the pathogenesis of nodal nevi, to answer these questions.

Clinical characteristics and survival data of melanoma patients with nevus cell aggregates within sentinel lymph nodes

Histopathologic differentiation of nevus cell aggregates and metastatic melanoma in lymph nodes is challenging. Patients with melanoma who had undergone sentinel lymph node (SLN) biopsy were evaluated using univariate and multivariate analyses as well as Kaplan-Meier statistics. Of the 651 patients, 50 (7.7%) had a nodal nevus in the SLN. In the logistic regression model, primary melanoma on the lower extremities proved to be the strongest independent negative predictor of nodal nevi with an odds ratio of 0.11 (95% confidence interval, 0.034-0.36; P = .0002). Overall 5-year survival (P = .17) and 5-year disease-free survival (P = .45) of patients with nodal nevi did not significantly differ from that of patients with negative SLNs. The frequency and anatomic localization of nodal nevi observed in the present study are in line with previous studies. Our 5-year survival data clearly demonstrate that nevus cell aggregates in lymph nodes have to be considered a benign condition even though it occurs in patients with melanoma. This study provides an indirect proof of validity and accuracy of current histopathologic methods for differentiation between nodal nevi and melanoma metastasis.

Clear cell nodular hidradenoma involving the lymphatic system: a tumor of uncertain malignant potential or a novel example of "metastasizing" benign tumor?

Exceedingly rare cases of neoplasms with clear-cut histopathologic features of benignity can show locoregional or even distant spread. Such cases can become putative examples of "benign metastasis" when a completely favorable clinical outcome is documented after an adequately long follow-up. We report 8 cases of morphologically benign clear cell nodular hidradenoma (CCNH) with lymphatic involvement. In 5 cases the cutaneous tumor showed small foci of intravascular deposits of neoplastic cells; in 2 cases the cutaneous tumor presented with a synchronous tumor in a regional node; in 1 case a nodal location CCNH was found with no evidence of any primary in the skin. All the cases were treated with conservative surgery and none of them showed disease progression during a follow-up period ranging from 2 to 11 years. These data suggest that in the absence of other histopathologic features of malignancy, lymphatic spread in CCNH can still carry an excellent prognosis and can be therefore considered as an example of "benign metastasis." As the latter concept can be set forth only after an uneventful long-term follow-up, in routine practice, cases of morphologically benign CCNH with lymphatic involvement are best labeled "atypical CCNH," or "CCNH-like tumor of uncertain malignant potential."