Morphometrical approach for predicting regional lymph node micrometastatic load in canine mast cell tumours: preliminary results

Abstract

Canine cutaneous mast cell tumours (MCTs) have a variable biologic behaviour, and accurate staging is necessary to dictate therapy and predict outcome. Regional lymph node (RLN) involvement is a relevant prognostic factor. While obvious lymph node (LN) metastases are relatively easy to be diagnosed, micrometastatic disease recognition is challenging. The main aim of the study was to evaluate the number of mast cells (MCs) in the LNs of clinically healthy dogs (n = 4, group 1), dogs with inflammatory diseases (n = 31, group 2) and dogs with cutaneous MCT (n = 27, group 3), including animals with no RLN metastases (subgroup 3.1), those with occasional MCs in RLNs (3.2) and those with obvious RLN metastasis (3.3). MCs also were morphometrically evaluated for the following nuclear parameters: mean nuclear area (MNA), mean nuclear perimeter (MNP), largest to smallest diameter length (LS ratio), mean nuclear form factor and coefficient of variation of nuclear area. The average percentages of MCs were 0.0 and 0.01 in groups 1 and 2, respectively, and 0.07, 2.4 and 47.1 in subgroup 3.1, 3.2 and 3.3. MNA and MNP were significantly higher in subgroup 3.3 than in group 2 (P < 0.05). MNA and MNP in subgroup 3.2 suggested the presence of neoplastic MCs; this prediction of micrometastatic load correlated with outcome. Analysis of preliminary results shows that nuclear morphometry is useful to detect micrometastatic disease in RLN of dogs bearing cutaneous MCTs.

Cytologic–histologic concordance in the diagnosis of neoplasia in canine and feline lymph nodes: a retrospective study of 367 cases

“…Other studies of mast cell metastasis have used cytologic criteria ranging from >3% mast cells with cellular pleomorphism, eosinophils and mast cell aggregates to >50% mast cells with several aggregates or pleomorphism . Morphometry also has been used to quantify mast cells in lymph node aspirates but the technique is not practical for routine cytologic examination . Histologic diagnoses also lacked consistency in assessing metastatic mast cell tumours in the present study, and uncertainty about the diagnosis was expressed in more than 25% of cases discrepant with cytology.…”

Comparison of mitotic index and Ki67 index in the prognostication of canine cutaneous mast cell tumours

“…As previously mentioned, the mitotic index is commonly included in the routine histopathology report of most commercial laboratories and therefore, in the authors' opinion, Ki67 index should be requested when the history (tumour growth pattern or presence of paraneoplastic syndromes), characteristic of the tumour (size, ulceration or degree of local inflammation) and mitotic index are discordant. Moreover, the authors would not recommend performing Ki67 index in dogs with lymph node metastasis (WHO stage II or III) or distant metastasis (WHO stage IV) because these cases have already been associated with a worse prognosis and further prognostic information is not likely to change the therapeutic approach. Conversely, investigating the proliferative activity of dogs with multiple MCTs, but no lymph node metastasis (WHO stage III) might be indicated because the overall prognosis depends on the characteristics of each individual tumour …”

Cytological lymph node evaluation in dogs with mast cell tumours: association with grade and survival*

“…This practice underscores the importance of developing accurate and reproducible criteria for the cytological evaluation of regional lymph nodes in dogs with mast cell tumours. A recent study evaluated the utility of several cytological evaluations of lymph node aspirates from dogs with and without mast cell tumours but did not give cytological criteria for diagnosing lymph node metastasis 22 . To the authors’ knowledge, specific cytological parameters to diagnose lymph node metastasis have not been evaluated or established.…”